The role of ERNDIM diagnostic proficiency schemes in improving the quality of diagnostic testing for inherited metabolic diseases

External quality assurance (EQA) is crucial to monitor and improve the quality of biochemical genetic testing. ERNDIM (www.erndim.org), established in 1994, aims at reliable and standardized procedures for diagnosis, treatment and monitoring of inherited metabolic disease (IMD) by providing EQA schemes and educational activities. Currently, ERNDIM provides 16 different EQA schemes including quantitative schemes for various metabolite groups, and interpretive schemes such as diagnostic proficiency testing (DPT). DPT schemes focus on the ability of laboratories to correctly identify and interpret abnormalities in authentic urine samples across a wide range of IMDs. In the DPT schemes, six samples each year are distributed together with clinical information. Laboratories choose and perform the tests needed to reach a diagnosis. Data were collected on 345 samples, distributed to up to 105 laboratories worldwide. Diagnostic proficiency (the % of total points possible for all participating laboratories within a scheme for analysis and interpretation) ranged widely: amino acid disorders (n = 20), range 33%-100%, mean 84%; organic acid disorders (n = 35), range 14%-100%, mean 84%; lysosomal storage disorders (n = 13), range 20%-97%, mean 73%; purine/pyrimidine disorders (n = 9), range 37%-100%, mean 70%; miscellaneous disorders (n = 8), range 17%-100%, mean 65%; no IMD, range 65%-95%, mean 85%. When a sample with the same disorder was distributed in a subsequent survey, performance improved in 75 cases with no improvement seen in 32, suggesting overall improvement of performance. ERNDIM diagnostic proficiency testing is a valuable activity which can help to assess laboratory performance, identify methodological/technical challenges, be informative during quality audits and contribute to a better clinical appreciation of diagnostic uncertainty.

Clinical Utility of the Ratio of Urinary Free Cortisol to Aldosterone as an Index for Inflammatory and Metabolic Dysregulation

OBJECTIVE

Urinary free cortisol (UFC) is a reliable marker to avoid cortisol fluctuation and the effects of binding proteins. However, UFC levels are affected by fluid intake and urine volume, and the normal levels range widely.

METHODS

To discover the utility of the ratio of urinary cortisol to aldosterone excretions, 246 patients in whom daily excretions of UFC and aldosterone (UAC) were measured were retrospectively analyzed.

RESULTS

The UFC/UAC ratio showed significant positive and negative correlations with the levels of serum cortisol (R=0.287) and aldosterone (R=-0.762), respectively. The UFC/UAC ratio increased with aging in female patients, while it was not altered by the level of BMI in either gender. Markers for metabolic and inflammatory status, including hemoglobin A1c (R=0.327), albumin (R=-0.331), C-reactive protein (R=0.317), ferritin (R=0.473), and D-dimer (R=0.569), showed correlations with the ratio of UFC/UAC that were more significant than the correlations with the serum level of cortisol or UFC alone. Of note, the UFC/UAC ratio was shown to be an indicator for the risk of diabetes (AUC: 0.765), hypoalbuminemia (0.839), hyper-CRPemia (0.748), and thrombophilia (0.824), in which the cut-off levels of the UFC/UAC ratio were around 12.

CONCLUSION

The UFC/UAC ratio is a variable for detecting metabolic and inflammatory complications related to adrenocortical dysfunction.

A resource of lipidomics and metabolomics data from individuals with undiagnosed diseases

Every year individuals experience symptoms that remain undiagnosed by healthcare providers. In the United States, these rare diseases are defined as a condition that affects fewer than 200,000 individuals. However, there are an estimated 7000 rare diseases, and there are an estimated 25-30 million Americans in total (7.6-9.2% of the population as of 2018) affected by such disorders. The NIH Common Fund Undiagnosed Diseases Network (UDN) seeks to provide diagnoses for individuals with undiagnosed disease. Mass spectrometry-based metabolomics and lipidomics analyses could advance the collective understanding of individual symptoms and advance diagnoses for individuals with heretofore undiagnosed disease. Here, we report the mass spectrometry-based metabolomics and lipidomics analyses of blood plasma, urine, and cerebrospinal fluid from 148 patients within the UDN and their families, as well as from a reference population of over 100 individuals with no known metabolic diseases. The raw and processed data are available to the research community so that they might be useful in the diagnoses of current or future patients suffering from undiagnosed disorders.

U-Shaped Associations Between Urinary Iodine Concentration and the Prevalence of Metabolic Disorders: A Cross-Sectional Study

Background: Iodine is important in both thyroid function and human metabolism. Studies have explored the effect of iodine on metabolic disorders through thyroid function. This study aimed to investigate the relationship between iodine status and metabolic disorders, such as metabolic syndrome (MetS), hypertension, impaired glucose metabolism, central obesity, and dyslipidemia. Methods: A total of 51,795 subjects aged ≥18 years from the TIDE (Thyroid Disorders, Iodine Status and Diabetes, a national epidemiological cross-sectional study) program were included. The prevalence of metabolic disorders and its related diseases was calculated based on the level of urinary iodine concentrations (UICs) using the chi-square method. To further explore whether the prevalence was associated with UIC, quadratic and UIC-stratified logistic regression models were used. Results: The prevalence of metabolic disorders as a function of UIC was found to be U-shaped with a lower prevalence of 76.0% at an UIC of 300-499 μg/L. Participants with an UIC of 300-499 μg/L showed an association with metabolic disorders (odds ratio [OR] = 0.857, 95% confidence interval [CI 0.796-0.922]) and hypertension (OR = 0.873 [CI 0.814-0.936]). An UIC of 300-799 μg/L was found to be associated with the occurrence of MetS and impaired glucose tolerance. An UIC of 500-799 μg/L was associated with the occurrence of prediabetes (OR = 0.883 [CI 0.797-0.978]). An UIC of ≥300 μg/L was associated with the occurrence of hypertriglyceridemia, hypercholesterolemia, and high levels of low-density lipoprotein cholesterol. Furthermore, an UIC of <100 μg/L showed an association with hypertension (OR = 1.097 [CI 1.035-1.162]) and hypercholesterolemia (OR = 1.178 [CI 1.117-1.242]). Conclusions: The association between UICs in adults and metabolic disorders and its related diseases is U-shaped. The association between UIC and metabolic disorders disappears in cases of iodine deficiency (<100 μg/L) or excess (≥500 μg/L).

Metabolic disorder of amino acids, fatty acids and purines reflects the decreases in oocyte quality and potential in sows

Oocyte quality is closely related to female fertility. Nevertheless, core nutritional metabolites influencing oocyte quality are unclear. Herein, comprehensive metabolomics analysis of follicular fluid, serum, and urine from low reproductive performance (LRP) and normal reproductive performance (NRP) sows was conducted. Twenty-seven, fourteen and sixteen metabolites (involved in metabolism of amino acids, fatty acids, purine and pyrimidine) were altered in follicular fluid, serum and urine, respectively, in LRP compared with NRP sows, and could decrease oocyte quality and developmental potential, ultimately leading to low fertility. Deoxyinosine, guanidine acetate, thymidine, 5,6-epoxy-eicosatrienoic acid, carnosine, docosahexaenoic acid and carbamoyl phosphate in follicular fluid, cysteine, carnitine, serotonin, hypoxanthine, valine and arginine in serum, as well as carnitine, phenyl glycine, N-acetyl glutamine, propionyl carnitine and choline in urine could be selected as diagnostic markers to indicate oocyte quality. Consistent with metabolomics data, we confirmed changes in concentrations of fatty acids and amino acids in follicular fluid. Targeting purine metabolism, elevating levels of deoxyinosine in in-vitro maturation medium of porcine oocyte significantly promoted the blastocyst rate. Collectively, this study provided new information of potential targets for predicting oocyte quality and developmental potential, and may help with strategies for early diagnosis or therapeutic/dietary intervention in improving reproductive outcomes.

Δ4-3-oxosteroid-5β-reductase deficiency: Responses to oral bile acid therapy and long-term outcomes

BACKGROUND

Disorders of primary bile acid synthesis may be life-threatening if undiagnosed, or not treated with primary bile acid replacement therapy. To date, there are few reports on the management and follow-up of patients with Δ4-3-oxosteroid 5β-reductase (AKR1D1) deficiency. We hypothesized that a retrospective analysis of the responses to oral bile acid replacement therapy with chenodeoxycholic acid (CDCA) in patients with this bile acid synthesis disorder will increase our understanding of the disease progression and permit evaluation of this treatment regimen as an alternative to the Food and Drug Administration (FDA) approved drug cholic acid, which is currently unavailable in China.

AIM

To evaluate the therapeutic responses of patients with AKR1D1 deficiency to oral bile acid therapy, specifically CDCA.

METHODS

Twelve patients with AKR1D1 deficiency, confirmed by fast atom bombardment ionization-mass spectrometry analysis of urine and by gene sequencing for mutations in AKR1D1, were treated with differing doses of CDCA or ursodeoxycholic acid (UDCA). The clinical and biochemical responses to therapy were monitored over a period ranging 0.5-6.4 years. Dose adjustment, to optimize the therapeutic dose, was based on changes in serum biochemistry parameters, notably liver function tests, and suppression of the urinary levels of atypical hepatotoxic 3-oxo-Δ4-bile acids measured by mass spectrometry.

RESULTS

Physical examination, serum biochemistry parameters, and sonographic findings improved in all 12 patients during bile acid therapy, except one who underwent liver transplantation. Urine bile acid analysis confirmed a significant reduction in atypical hepatotoxic 3-oxo-Δ4 bile acids concomitant with clinical and biochemical improvements in those patients treated with CDCA. UDCA was ineffective in down-regulating endogenous bile acid synthesis as evidenced from the inability to suppress the urinary excretion of atypical 3-oxo-Δ4-bile acids. The dose of CDCA required for optimal clinical and biochemical responses varied from 5.5-10 mg/kg per day among patients based on maximum suppression of the atypical bile acids and improvement in serum biochemistry parameters, and careful titration of the dose was necessary to avoid side effects from CDCA.

CONCLUSION

The primary bile acid CDCA is effective in treating AKR1D1 deficiency but the therapeutic dose requires individualized optimization. UDCA is not recommended for long-term management.

Association of urinary concentrations of four chlorophenol pesticides with cardiometabolic risk factors and obesity in children and adolescents

This study was undertaken to determine the association of four chlorophenol pesticides with cardiometabolic risk factors and obesity in children and adolescents. This cross-sectional study was conducted in 2016 on 242 children and adolescents, aged 6 to 18 years. The concentrations of 2,4-dichlorophenol (2,4-DCP), 2,5-dichlorophenol (2,5-DCP), 2,4,5-trichlorophenol (2,4,5-TCP), and 2,4,6-trichlorophenol (2,4,6-TCP) in the urine were examined and their association with indices of obesity and cardiometabolic risk factors was determined. Multivariate linear regression and multinomial logistic regression analyses were applied. Overall, 242 participants with mean (SD) ages of 11.3 (2.5) years completed the survey. After adjustment for confounders, a significant positive association was found between body mass index (BMI) z-score and waist circumference (WC) with 2,5-DCP (0.07 (95% CI 0.04, 0.1)) and 0.79 (95% CI 0.54, 1.03), respectively. A significant association of 2,4,5-TCP was only found with WC (0.23 (95% CI 0.0, 0.46), but the relationship with 2,4-DCP was not significant. 2,5-DCP had a significant relationship only with obesity (1.09 (95% CI 1.1, 1.19)), while 2,4-DCP and 2,4,5-TCP showed no significant correlation with overweight or obesity. 2,4-DCP showed a significant positive relationship with high density lipoprotein-cholesterol (HDL-C). Moreover, 2,5-DCP showed a significant negative relationship only with systolic blood pressure and 2,4,5-TCP had a statistically significant inverse association with total cholesterol and HDL-C (-0.71 (95% CI -0.98, -0.45)). This study suggests potential associations of chlorophenol pesticides with overweight, obesity, lipid profile, and blood pressure in children and adolescents. Longitudinal studies are necessary to assess the clinical impact of these findings.

Qualitative urinary organic acid analysis: 10 years of quality assurance

Over the last 10 years, a total of 90 urine samples from patients with metabolic disorders and controls were circulated to different laboratories in Europe and overseas, starting with 67 laboratories in 2005 and reaching 101 in 2014. The participants were asked to analyse the samples in their usual way and to prepare a report as if to a non-specialist pediatrician. The performance for the detection of fumarase deficiency, glutaric aciduria type I, isovaleric aciduria, methylmalonic aciduria, mevalonic aciduria, phenylketonuria and propionic aciduria was excellent (98-100 %). Over the last few years, detection has clearly improved for tyrosinaemia type I (39 % in 2008 to over 80 % in 2011/2014), maple syrup urine disease (85 % in 2005 to 98 % in 2012), hawkinsinuria (62 % in 2010 to 88 % in 2014), aminoacylase I deficiency (43 % in 2009 to 73 % in 2012) and 3-methylcrotonyl-CoA carboxylase deficiency (60 % in 2005 to 93 % by 2011). Normal urines were mostly considered as normal (83-100 %), but laboratories often made additional diagnostic suggestions. When the findings were unambiguous, the reports were mostly clear. However, when they were less obvious, the content and quality of reports varied greatly. Repetition of organic acid measurements on a fresh sample was rarely suggested, while more complex or invasive diagnostic strategies, including further metabolic screening or biopsy were recommended. Surprisingly very few participants suggested referral from the general paediatrician to a specialist metabolic centre to confirm a diagnosis and, if applicable, to initiate treatment despite evidence suggesting that this improves the outcome for patients with inherited metabolic disorders. The reliability of qualitative organic acid analysis has improved over the last few years. However, several aspects of reporting to non-specialists may need discussion and clinicians need to be aware of the uncertainty inherent in all forms of laboratory diagnostic analysis.

Crystalluria

Crystalluria is a marker of urine supersaturation with substances deriving from metabolic disorders, inherited diseases or drugs. The investigation of crystalluria must be done according to a protocol which includes the delivery to the laboratory of a proper urine sample, the use of a microscope equipped with polarized light, the accurate knowledge of urine pH, and a comprehensive examination of the crystals, which is based on their identification, quantification and size measurement. For unusual crystals, infrared spectroscopy may also be needed. The main urinary crystalline categories include: calcium oxalates, calcium phosphates, uric acids and urates, struvite, aminoacids (cystine), purines (2,8-dihydroxyadenine and xanthine) and drugs (e.g. sulfamethoxazole, amoxycillin, ceftriaxone, atazanavir). The investigation of crystalluria is a cheap and valuable tool for the detection and the monitoring of inherited and acquired diseases associated with urinary stone formation or renal function impairment - either acute or chronic - due to intrarenal crystal precipitation.

[Quantitative mineralogical analyzes of kidney stones and diagnosing metabolic disorders in female patients with calcium oxalate urolithiasis]

OBJECTIVE

To conduct a complex examination of female patients with calcium oxalate urolithiasis to detect metabolic disorders, leading to stone formation.

MATERIALS AND METHODS

The study was carried out using complex physical and chemical methods, including quantitative X-ray phase analysis of urinary stones, pH measurement, volumetry, urine and blood spectrophotometry.

RESULTS

Quantitative mineralogical composition of stones, daily urine pH profile, daily urinary excretion of ions of calcium, magnesium, oxalate, phosphate, citrate and uric acid were determined in 20 female patients with calcium oxalate stones.

DISCUSSION

We have shown that most of the stones comprised calcium oxalate monohydrate or mixtures of calcium oxalate dihydrate and hydroxyapatite. Among the identified abnormalities, the most frequent were hypocitraturia and hypercalciuria - 90 and 45%, respectively. Our findings revealed that the daily secretion of citrate and oxalate in patients older than 50 years was significantly lower than in younger patients.

SUMMARY AND CONCLUSION

In conclusion, daily urinary citrate excretion should be measured in female patients with calcium oxalate stones. This is necessary both to determine the causes of stone formation, and to monitor the effectiveness of citrate therapy.

The Influence of Urinary Concentrations of Organophosphate Metabolites on the Relationship between BMI and Cardiometabolic Health Risk

The objective was to determine whether detectable levels of OP metabolites influence the relationship between BMI and cardiometabolic health. This cross-sectional study was conducted using 2227 adults from the 1999-2008 NHANES datasets. Urinary concentrations of six dialkyl phosphate metabolites were dichotomized to above and below the detection limit. Weighted multiple regression analysis was performed adjusting for confounding variables. Independent of BMI, individuals with detectable metabolites had higher diastolic blood pressure (for dimethylphosphate, diethylphosphate, and diethyldithiophosphate; P < 0.05), lower HDL (for diethyldithiophosphate; P = 0.02), and higher triglyceride (for dimethyldithiophosphate; P = 0.05) than those below detection. Contrarily, those with detectable dimethylthiophosphate had better LDL, HDL, and total cholesterol, independent of BMI. Individuals at a higher BMI range who had detectable diethylphosphate (interaction: P = 0.03) and diethylthiophosphate (interaction: P = 0.02) exhibited lower HDL, while little difference existed between OP metabolite detection statuses at lower BMIs. Similarly, individuals with high BMIs and detectable diethylphosphate had higher triglyceride than those without detectable levels, while minimal differences between diethylphosphate detection statuses were observed at lower BMIs (interaction: P = 0.02). Thus, cardiometabolic health outcome differs depending on the specific OP metabolite being examined, with higher BMIs amplifying health risk.

Atherogenic lipids and vascular complications in a selected diabetic population with normal urinary albumin/creatinine ratios

OBJECTIVE

To test the hypothesis that at different urinary albumin/creatinine ratios within the normal ranges, diabetics have low but similar prevalence of metabolic and micro vascular disease.

METHODS

The study sample consisted of normotensive diabetics not taking any medications known to effect blood pressure and lipids. The data were collected from the Diabetes Register. The diabetics were subgrouped according to the urinary albumin/creatinine ratios. MA is defined as present if the albumin/creatinine ratio (ACR) is more than 2 mg/mmol.

RESULTS

MA was present in 16% of the 152 diabetics. Total cholesterol, systolic BP, and triglycerides were significantly high in diabetics with ACR≥1<2 compared with <1. The prevalence rates for retinopathy and neuropathy in the MA group were also significantly high. However, a large number of diabetics without MA had had established complications (37% retinopathy, 40% neuropathy, and 16% peripheral vascular disease). Because these results were based on single early morning urine samples, we looked at their MA in the past year. After exclusion of regressed and progressed groups, the complications rate remained the same.

CONCLUSION

The high prevalence of metabolic and vascular complications seen even in absence of MA indicates an early intervention and those diabetics should not wait unitl CVD risk scores raise to receive preventive treatment.

[Clinical value of the determination of markers for endothelial dysfunction (endothelin-1, microalbuminuria) and tubulointerstitial tissue lesion (β2-microglobulin, monocyte chemotactic protein-1) in hypertensive patients with uric acid metabolic disorders]

AIM

To identify the risk factors of kidney injuries in hypertensive patients with uric acid (UA) metabolic disorders in order to choose the optimal management tactics, by analyzing the changes in markers for endothelial dysfunction (endothelin-1 (ET-1), microalbuminuria (MAU), intima-media thickness (IMT)) and tubulointerstitial tissue lesion (beta2-microglobulin (beta2-MG, monocyte chemotactic protein-1 (MCP-1)).

SUBJECTS AND METHODS

Eighty-one patients with grade 1 hypertension without associated diseases, diabetes mellitus, or metabolic syndrome were examined. There were 3 study groups: 1) hyperuricosuria (n = 7); 2) hyperuricemia (n = 53); 3) hyperuricemia and renal failure (n = 6); and a control group of 15 hypertensive patients without UA metabolic disorders who were matched for age and gender with the patients of the study groups.

RESULTS

The hypertensive patients with hyperuricemia, as compared with those without UA metabolic disorders, showed higher plasma concentrations of ET-1 (p = 0.003) and MAU (p = 0.009) and more marked increases in common carotid IMT (p = 0.044), urinary excretion of beta2-MG (p = 0.010), and MCP-1 (p = 0.030). There were direct correlations between all the examined biomarkers and the degree of uricemia (Rs = 0.453; p < 0.001; Rs = 0.411; p < 0.001; Rs = 0.322; p = 0.067; Rs = 0.537; p < 0.001; and Rs = 0.318; p = 0.004, respectively) and between the markers of endothelial dysfunction and those of tubulointerstitial tissue lesion (Rs = 0.295 for ET-1 and MCP-1; p = 0.008; Rs = 0.399 for ET-1 and beta2-MG; p < 0.001; Rs = 0.462 for MAU and beta2-MG; p < 0.001; and Rs = 0.188 for MAU and MCP-1; p = 0.094). Multivariate analysis of the clinical and laboratory parameters under study confirmed the role of serum MCP-1, beta2-MG, MAU, creatinine levels as independent predictors for decreased relative urinary gravity, the clinical sign of tubulointerstitial tissue lesion/fibrosis, and that of a wider range of the indicators, such as MAU, ventricular septal thickness, glomerular filtration rate, relative urinary gravity, systolic blood pressure, MPC-1, low-density lipoproteins, as risk factors for renal filtrating dysfunction.

Detection of acylglycines in urine by 1H and 13C NMR for the diagnosis of inborn metabolic diseases

A range of inborn metabolic diseases result in abnormal accumulation of acylglycines in body fluids. Therefore, detection of these metabolites is important for diagnostic purposes. (1)H and (13)C NMR spectroscopies have successfully been applied for both qualitative and quantitative determinations of various acylglycines in urine samples from patients suffering from metabolic diseases connected with excretion of these compounds. Various acylglycines were identified in test urine samples from 15 patients suffering from five different metabolic diseases, providing information which could be crucial for their diagnoses. The paper reports complete (1)H and (13)C NMR data of 11 acylglycines, which is essential for this type of NMR analysis of body fluids. NMR spectroscopy has been proven effective in determining the presence as well as the levels of acylglycines in urine. The proposed method is rapid, simple and requires minimal sample treatment.

Uric acid excretion in healthy subjects: a nomogram to assess the mechanisms underlying purine metabolic disorders

The reference range for urinary uric acid excretion has not been precisely defined. Different urinary variables have been proposed to determine the renal contribution to increased or decreased serum urate concentrations. We examined which urinary variable best indicates uric acid excretion over a wide range of serum urate concentrations. Purine metabolism was studied in 10 healthy male subjects (aged 26-58 years) both at their endogenous normal serum urate levels (normouricemic state) and after the oral administration of allopurinol (300 mg/24 h for 5 days) and ribonucleic acid (4 g/8 h for 4 days) to decrease (hypouricemic state) and increase (hyperuricemic state) serum urate concentrations, respectively. The results from patients with several conditions known to affect uric acid synthesis and/or the renal excretion of uric acid were used to validate a constructed nomogram. Over a wide range of mean serum urate levels (from 2.7 to 9.5 mg/dL) and mean 24-hour urinary uric acid excretion (171 to 1368 mg/[24 h 1.73 m(2)]), the highest correlation coefficient between serum urate and uric acid excretion was obtained for the 24-hour uric acid determination (r = 0.928; P < .001). The constructed nomogram allowed the definition of the mechanism underlying hyperuricemia and hypouricemia in patients with a myriad of diseases known to affect purine metabolism. The urinary variable that best correlates with a wide range of serum urate concentrations is 24-hour urinary uric acid excretion. The constructed nomogram allows the identification of the kidney contribution to a given purine metabolic abnormality.

Spot urine potassium as a potential screening test for aldosterone breakthrough

BACKGROUND AND AIMS

Treatment with angiotensin converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) may suppress aldosterone production only in the initial phase of treatment and subsequently lead to a rising level of aldosterone to baseline or higher. This phenomenon is described as aldosterone breakthrough. Apart from serial plasma aldosterone levels, there are no other test to identify this condition. The purpose of this study was to evaluate the role of spot urine potassium as a potential screening test for aldosterone breakthrough.

MATERIALS AND METHODS

This was a cross sectional study involving 94 patients who were on an ACEI or ARB for a minimum duration of 40 weeks. An aldosterone cut off value of 102 pg/ml was used to define aldosterone breakthrough based on a previous study. Patients with primary hyperaldosteronism, conditions giving rise to secondary hyperaldosteronism and those who were on drugs which could interfere with the renin-angiotensin-aldosterone system were excluded. The study patients had their blood sample analysed for renal profile, renin, aldosterone and urine sample analysed for urine potassium.

RESULTS

Incidence of aldosterone breakthrough in this study was 23.4%. The median urine potassium was 62.0 mmol/L in the aldosterone breakthrough group compared to the non-breakthrough group which was 38.5 mmol/L. The urine potassium showed statistically significant difference between both groups (p=0.016). The correlation coefficient was 0.284; statistically significant (p=0.006) as the sample size was large (n=94).

CONCLUSION

A raised urinary potassium after initiating treatment ith ACEI or ARB is a potential screening test for aldosterone breakthrough.

Clinical manifestations and etiology of renal stones in children less than 14 years age

Urolithiasis is one of the commonest problems in pediatric nephrology. Prevalence of urolithiasis in pediatric patients is increasing. The purpose was to properly diagnose and treat with the special attention to the risk factors. This study is case-series and was performed on 100 pediatric patients for evaluation of clinical manifestation and etiology of renal stone in Qom. Hundred Children, fewer than 14 years old with mean age of 3.32 years, were included (54% male). Etiology of urolithiasis in 5% was unclear. Metabolic disorders found in patients were mainly: Hypocitraturia in 54, hyperoxaluria in 14, hyperuricosuria in 25, cystinuria in 6, hypercalciuria in 28 and phosphaturia in 8 patients. The main clinical presentation was fever, pain, irritability, dysuria and hematuria. Family history of urolithiasis was found in 23% of patients and 54% presented with urinary tract infection (UTI). We conclude that majority of patients were symptomatic and hypocitraturia was the commenest risk factor among others.

Metabolic and physico-chemical urolithiasis parameters in the first morning urine

The 24-hour urine is golden standard for metabolic assessment of stone formers. However, due to the difficulties in collecting almost 1/3 of the samples can not be used for the analysis. Therefore, we analyzed first morning urine and calculated different risk indexes in order to asses possibility of using it in determining urolithiasis risk. Subjects were divided into 4 groups: male patients (n = 31, age 18-64), female patients (n = 31, age 25-63), male controls (n = 16, age 25-64) and female controls (n = 19, age 21-65). First morning urine pH, concentrations of calcium, magnesium, phosphate, sodium, potassium, chloride, citrate, urate, oxalate, creatinine and glycosaminoglycans were determined. Based on them, ionic concentrations and activity products of calcium oxalate and phosphate were calculated by EQUIL 2. In addition, different risk indices were calculated. The results showed that both patients and control groups had metabolic disorders, but the frequencies of occurrence were statistically independent. Significant difference in concentration of urinary constituents between corresponding patient and control groups was observed only for glycosaminoglycans in female subjects. Ca/Cit ratio and Baggio index could differentiate between both corresponding patients and control groups. The results indicate that interplay between stone formation inhibitors and promotors is responsible for urinary stone formation and that the first morning urine could be used in assessing urolithiasis risk and its prevention.

Quality of analytical performance in inherited metabolic disorders: the role of ERNDIM

External quality assurance (EQA) schemes are essential for improvement of accuracy, reliability and comparability of results of biochemical genetic tests. ERNDIM (European Research Network for evaluation and improvement of screening, Diagnosis and treatment of Inherited disorders of Metabolism), established in 1994, operates nine EQA schemes for biochemical genetic testing according to international norms and recommendations. These comprise qualitative schemes for amino acids, organic acids, purines and pyrimidines, special assays in serum and urine and white cell cystine, qualitative organic acid and acylcarnitine schemes, as well as diagnostic proficiency testing. The total number of participants has increased from 123 in 1994 to 268 in 2007. Additional activities include participation in the Eurogentest project, a laboratory directory, training, education and development of guidelines. Results from the quantitative amino acid scheme with 170 participants reveal good variation within and between laboratories of below 10% for 10 amino acids; good within-laboratory variation but intermediate inter-laboratory variation of 10-22% for 11 amino acids; and higher variation within and between laboratories for 8 amino acids. Results on samples from 51 inherited metabolic disorders from two of five centres organizing diagnostic proficiency testing indicate overall diagnostic efficiency above 80% and improved performance of individual laboratories. Comparison of results for 10 and 12 compounds in the serum and urine special assay schemes respectively for 2000 and 2007 reveal clear improvement of precision within laboratories and in inter-laboratory variation. There is considerable evidence that performance in biochemical genetic testing has improved since the introduction of ERNDIM schemes.

Qualitative urinary organic acid analysis: methodological approaches and performance

A programme for proficiency testing of biochemical genetics laboratories undertaking urinary qualitative organic acid analysis and its results for 50 samples examined for factors contributing to poor performance are described. Urine samples from patients in whom inherited metabolic disorders have been confirmed as well as control urines were circulated to participants and the results from 94 laboratories were evaluated. Laboratories showed variability both in terms of their individual performance and on a disease-specific basis. In general, conditions including methylmalonic aciduria, propionic aciduria, isovaleric aciduria, mevalonic aciduria, Canavan disease and 3-methylcrotonyl-CoA carboxylase were readily identified. Detection was poorer for other diseases such as glutaric aciduria type II, glyceric aciduria and, in one sample, 3-methylcrotonyl-CoA carboxylase deficiency. To identify the factors that allow some laboratories to perform well on a consistent basis while others perform badly, we devised a questionnaire and compared the responses with the results for performance in the scheme. A trend towards better performance could be demonstrated for those laboratories that regularly use internal quality control (QC) samples in their sample preparation (p = 0.079) and those that participate in further external quality assurance (EQA) schemes (p = 0,040). Clinicians who depend upon these diagnostic services to identify patients with these defects and the laboratories that provide them should be aware of the potential for missed diagnoses and the factors that may lead to improved performance.

Outcome of organic acidurias in China

From June 1998 to May 2007, 9566 urine samples were collected from patients with psychomotor deficits, seizures, vomiting and unconsciousness in Peking University First Hospital. Their urine organic acids profiles were analysed using gas chromatography - mass spectrometry (GCMS), GCMS solution and Inborn Errors of Metabolism Screening System software. In all patients, blood acylcarnitines were analysed using tandem mass spectrometry. One hundred and sixty-eight patients (1.76%) with organic acidurias were detected. Among them, 116 (116/ 168, 69.0%) had methylmalonic aciduria, 63 (54.3%) of these 116 patients had methylmalonic aciduria combined with homocysteinemia. Sixteen (9.5%) of those patients detected with organic acidurias had propionic aciduria, and 15 (8.9%) had multiple carboxylase deficiency. Seven (4.2%) had glutaric aciduria type 1. After dietary treatment, medicine and rehabilitation, clinical improvements were observed in more than half of the patients. Twenty-eight of the 168 patients (16.7%) recovered and led a normal life. The method of urine organic acid analysis by gas chromatography - mass spectrometry and blood acylcarnitines analysis by tandem mass spectrometry have been established and applied successfully in China, namely Beijing, Shanghai, Wuhan and Guangzhou. The prognoses of Chinese patients with organic acidurias have also improved significantly.

Comparison of tetrahydrofuran and ethyl acetate as extraction solvents for urinary organic acid analysis

The analysis of urinary organic acids is crucial for the diagnosis of many inborn errors of metabolism. A vital part of the analytical process is the extraction procedure. The sensitivity and linearity of the analysis of 26 diagnostically important urinary metabolites with tetrahydrofuran (THF) and ethyl acetate (EtOAc) as extraction solvents were determined by gas chromatography-mass spectrometry. Good linearity (r (2) > 0.90) was observed for all of the compounds in the investigated concentration range (290-900 mumol/L) for both solvents. For less polar compounds, THF extraction yielded lower or similar sensitivities as compared with EtOAc (sensitivity ratio: 0.6-1.3). For more polar compounds, however, much higher sensitivities were observed when THF was used (sensitivity ratio: 1.8-17.2). Our results provide information concerning the use of THF for the sensitive quantitative analysis of polar urinary metabolites which are difficult to quantify using EtOAc.

Investigation of a wide spectrum of inherited metabolic disorders by 13C NMR spectroscopy

High-resolution (1)H NMR spectroscopy of body fluids has proved to be very useful in diagnostics of inherited metabolic diseases, whereas (13)C NMR remains almost unexploited. In this paper the application of (13)C NMR spectroscopy of fivefold concentrated urine samples for diagnosis of selected metabolic diseases is reported. Various marker metabolites were identified in test urine samples from 33 patients suffering from 10 different diseases, providing information which could be crucial for their diagnoses. Spectra were accumulated for 2 h or overnight when using spectrometers operating at 9.4 or 4.7 T magnetic fields, respectively. Interpretation of the measurement results was based on a comparison of the peak positions in the measured spectrum with reference data. The paper contains a table with (13)C NMR chemical shifts of 73 standard compounds. The method can be applied individually or as an auxiliary technique to (1)H NMR or any other analytical method.

Two elderly patients with mineralocorticoid excess due to 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) impairment

A 75-year-old woman had a low circulating level of aldosterone, despite the mineralocorticoid excess state. These abnormalities were improved by spironolactone administration. The distinct elevation of urinary cortisol/cortisone ratio revealed 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) impairment. Moreover, slight but distinct elevation of the ratio was found in a 95-year-old woman with normotension and normopotassemia. The mineralocorticoid excess state with reduced aldosterone level appeared following with vomiting and diarrhea, exaggerating asymptomatic impairment of 11beta-HSD2 to induce apparent mineralocorticoid excess (AME)-like condition.

Study of spontaneous crystalluria on a series of patients in the Tadla Azilal Moroccan area

OBJECTIVES

There are few studies on crystalluria in the developing countries. The aim of the present study was carrying out a first study in Morocco on the frequency and the chemical nature of the crystalluria according to the sex and the age of human individuals living in the Tadla Azilal moroccan area.

METHOD

200 samples resulting from the morning urines of morning fasting individuals of the two sexes and different ages were collected. The pH was measured by a portable pH-meter "Pocket pH-meter ad 170 pH". The identification of the chemical nature of the crystalluria was carried out using a polarized light microscope "Olympus BX41". Such identification was based on morphology, polarization, and the pH of the urinary crystals.

RESULTS

In this series the positive frequency of crystalluria was 25.4% and was distributed on 3 age groups so that 27.9% in the youngest group, 32.6% in the middle aged group and 39.5% in the oldest one. The distribution on the sex is such as 53.4% in the man and 46.5% in the woman. A large majority (83.7%) of the crystalluria consists of homogeneous crystalluria. In the man, the Weddellite is dominant (69.6%) in the crystalluria while in the woman the Weddellite yields the place to the two phases of the uric acid (60%).

CONCLUSIONS

The studied series presents a non high frequency of crystalluria, which increases with the age. The factor sex has weakly increased the frequency of crystalluria in the man compared to the woman. The oxalocalcic nature is dominant in the crystalluria resulting from the man while it is the uric nature that is so in the woman. Other studies are necessary to be able to understand the etiology of a such difference, in the chemical nature of the crystalluria, between the two sexes.

Medical evaluation and treatment of urolithiasis

Nephrolithiasis is responsible for 1 in 1000 to 1 in 7600 pediatric hospital admissions annually throughout the United States. Seventy-five percent of children with nephrolithiasis have an identifiable predisposition to stone formation. This article reviews the different causes and disease states associated with nephrolithiasis in the pediatric population. The initial evaluation and the metabolic evaluation of children with nephrolithiasis are reviewed. Treatment modalities for the different stone types are also described.

Diffusion-weighted MR imaging and MR spectroscopy in glutaric aciduria type 1

Although conventional magnetic resonance imaging (MRI) findings of glutaric aciduria type 1 (GA-1) have been well established, diffusion weighted MR imaging (DWI) and proton MR spectroscopy (MRS) findings are limited. We report widespread restricted diffusion in the white matter and increased diffusion in bilateral putamen in a case of GA-1. The MRS showed decreased N-acetyl-aspartate (NAA)/creatine (Cr) ratio compared with a sex and age-matched control with no significant change in choline (Cho)/Cr ratio. The presence of the lactate peak reflecting disturbed mitochondrial functions in this disease has never been reported.

0,2An cross-ring cleavage as a general diagnostic tool for glycan assignment in glycoconjugate mixtures

In contrast to proteomics significantly less efficient analytical tools are presently available for high throughput glycomics using mass spectrometry. In this article, a strategy to use the (0,2)A(n) ring cleavage ion at the reducing end of free glycans as a diagnostic ion for assignment of free glycans, in presence of glycopeptides containing similar glycosylation patterns, is presented for rapid distinction in complex mixtures by mass spectrometry. The MS to MS/MS automatic switching, already previously introduced for the on-line LC-MS and CE-MS analysis, is shown in this contribution to be highly functional to obtain diagnostic fragmentation patterns of free glycan precursors in rapid screening of highly complex glycoconjugate mixtures obtained from clinical samples, namely from the urine of patients suffering from congenital disorders of glycosylation. Congenital disorders of glycosylation (CDG) are inherited metabolic diseases based on defects in the glycosylation pathways of glycoconjugates. The urine of CDG patients was reported to contain O-glycans and glycosylated amino acids at concentrations two to three orders of magnitude higher in comparison with the healthy control, characterized by a high degree of heterogeneity concerning the type, number, and values of molecular ions. Using the (0,2)A(n) ring cleavage ion approach by tandem MS, it was possible to sort out free glycans and get them assigned.

[Effect of L-carnitine on metabolic disorders in rats with experimental acyl-CoA dehydrogenase deficiency]

Effect of L-carnitine (LC) on the metabolism of organic acids and carnitine homeostasis was studied in rats with riboflavin deficiency producing unusual dicarboxylic acidurea and modeling multiple acyl-CoA dehydrogenase deficiency in humans. Riboflavin deficient (RFD) rats exhibited increased excretion of glutaric, ethylmalonic, and methylsuccinic acids, as well as isovaleryl-, butyryl-, isobutyryl-, 2-methyl-butyryl-, and hexanoylglycine, short-chain and medium-chain saturated, and unsaturated dicarboxylic organic acids (C6-C10). RFD rats also showed a decrease in the concentration of free LC in the blood plasma and in tissues, an increase in the level of isobutyryl- and isovalerylcarnitine in muscle tissue, and reduction in the level of acetyl- and propionylcarnitine in the blood plasma, kidney, and liver (all changes detected relative to animals in the control group). The introduction of LC to RFD rats normalized the LC homeostasis by increasing free LC concentration in the blood plasma and tissues, enhanced the acyl-LC excretion with urine and the level in tissues, and reduced the manifestations of organic acidurea.

[Bicarbonate calcium mineral water with carbon dioxide in rehabilitation of children with dismetabolic nephropathies complicated by renal inflammation]

A renal function was studied in children with dismetabolic nephropathy and renal inflammation before and after spa treatment with low-mineral water from the spring "Gornovodnoye". Drinking the water resulted in intensification of 24-h diuresis in increasing proportion of sodium and chlorine ions concentrations and decreasing proportion of calcium and magnesium ions concentrations. A membrane-stabilizing action of Gornovodnenskaya mineral water reduced oxaluria and uraturia. An effective scheme of balneotherapy is proposed.

The W258X mutation in SLC22A12 is the predominant cause of Japanese renal hypouricemia

Recently, a urate transporter, hURAT1 (human uric acid transporter 1) encoded by SLC22A12, was isolated from the human kidney. hURAT1 is presumed to play the central role in reabsorption of urate from glomerular filtrate. In the present study, we analyzed SLC22A12 in seven unrelated Japanese patients with renal hypouricemia whose serum level of urate was less than 1.0 mg/dl, and their family members. We performed direct DNA sequencing of the exon and exon-intron boundaries of SLC22A12 using genomic DNA. Six of the seven patients (86%) possess mutations in SLC22A12. In five patients, a homozygous G to A transition at nucleotide 774 within exon 4 of SLC22A12, which forms a stop codon (TGA) at codon 258 (TGG), was identified (W258X). In one patient, the C to T transition within exon 3, which changes threonine at codon 217 to methionine (T217 M), and the W258X mutation were found (compound heterozygote). Thus, among 12 mutational alleles in six patients, 11 were the W258 X mutation (92%). Family members with the heterozygous W258X mutation (carriers) show relatively low levels of serum urate. The present study demonstrates that homozygous W258X mutation is the predominant genetic cause of idiopathic renal hypouricemia in Japanese patients.

[Hemopyrrollactamuria (HPU); from spots to pseudo-disease]

In recent years, patients in the Netherlands confront their doctors with the diagnosis 'haemopyrollactamuria' (HPU), based on the presence of the haemopyrrollactam complex in their urine. The diagnosis is made by a commercial laboratory in the Netherlands (www.keac.nl). We have not been able to find peer-reviewed scientific literature on this metabolic disease. The haemopyrrollactam complex represents the so-called mauve spot, which was the subject of much controversy in schizophrenia research in the previous century. Reviewing all of the available data, we feel that HPU should be classified as a pseudo-disease.

Metabolic findings after colocystoplasty in children

OBJECTIVES

To investigate whether colocystoplasty has resulted in metabolic changes in the growing child during long-term follow-up according to whether cecum with ascending or sigmoid colon was used.

METHODS

Twenty-eight patients (mean age at surgery 11 years) were included in the study and divided into two groups: group 1, cystoplasty with cecum and ascending colon (12 patients) and group 2, sigmoid cystoplasty (16 patients). Patients' linear growth, body mass index, and the following parameters were estimated before surgery and at 3, 6, and 12 months, and then yearly after surgery: blood and urine electrolytes (sodium, potassium, chloride, calcium, phosphorus, magnesium), creatinine, urea, blood gases, blood pH, urine pH, and blood alkaline phosphatase (ALP). All the data were statistically analyzed.

RESULTS

In group 1, the blood ALP increased significantly (P = 0.026) during follow-up. Severe metabolic acidosis with or without hyperchloremia was found in 7 patients. In group 2, the serum sodium and serum calcium levels decreased significantly (P = 0.014 and P = 0.003, respectively); however, the blood ALP, urine sodium, and urine phosphorus levels increased significantly (P = 0.033, P = 0.027, and P = 0.026, respectively) during follow-up. A statistically significant decrease in blood pH (P = 0.022) was found after surgery. Severe metabolic acidosis with or without hyperchloremia was detected in 5 patients. The average linear growth decreased significantly (P = 0.001 and P = 0.016, respectively) 1 and 2 years postoperatively.

CONCLUSIONS

The statistically significant increase in blood ALP and decrease in serum calcium indicate bone demineralization after colocystoplasty. Our investigations in children suggest that bone demineralization is more frequent after sigmoid cystoplasty than after the use of cecum and ascending colon.

[Application of gas chromatography-mass spectrometry analysis on urine filter paper in the high-risk screening and diagnosis of inherited metabolic diseases]

OBJECTIVE

To establish a specific procedure for the high-risk screening and diagnosis of organic acidurias and other inherited metabolic diseases in China.

METHODS

A nation-wide network for the high-risk screening and diagnosis of genetic metabolic diseases was formed to facilitate the collaboration. Urine samples were collected using filter paper from patients with clinical symptoms suspicious of inherited metabolic diseases. The samples were eluted with distilled water and internal standards were added. Samples were treated with hydroxylamine hydrochloride to form oximes to improve the recoveries of 2-ketoacids. Urinary organic acids were extracted with ethyl acetate and diethyl ether under acidic condition. After dehydration, the combined organic phase was evaporated to dryness with nitrogen. The residues were added with BSTFA + 1%TMCS and heat incubated to form the trimethylsilyl derivatives, and then were analyzed on an Agilent 5890/5973N gas chromatography-mass spectrometer (GC-MS), with a 7683 series auto-sampler. The peaks were identified by reference to a mass spectral library.

RESULTS

Totally 352 samples were collected from the network collaborating hospitals since 2001. Thirty-four (9.66%) cases of various inherited metabolic diseases were diagnosed with an age range of 2 days to 14 years. The disease profile was consisted of methylmalonic acidemias (6), alpha-keto-glutaric aciduria (5), tyrosinemia type I (4), dicarboxylic aciduria (4), multiple carboxylase deficiency (3), phenylketonuria (3), lactic acidemia (3), propionic acidemia (2), ornithine transcarbamoylase deficiency (1), ethylmalonic-adipic aciduria (1), glutaric aciduria type II (1) and 3-methylcrotyl CoA carboxylase deficiency (1). The most common clinical symptoms and signs included mental and developmental retardation, convulsion, musculotonic abnormality and jaundice. Routine laboratory tests often revealed metabolic acidosis, hypoglycemia and hyperammonemia, etc.

CONCLUSION

Urine organic acids analysis by GC-MS remains to be the most important technique for the high-risk screening and diagnosis of inherited metabolic diseases. Use of urine filter paper for sample collection and analysis in advanced genetic metabolic centers is a practical approach to extend the diagnostic capacity and improve the management of such diseases in China. Collaborative network played a critical role in the success of the program.

[Primary trimethylaminuria or fish odor syndrome. A novel mutation in the first documented case in Spain]

BACKGROUND AND OBJECTIVE

Trimethylaminuria or fish odor syndrome is a metabolic disorder characterized by a failure in the oxidation route from trimethylamine (TMA) to trimethylamineN-oxide (TMA-O). Primary trimethylaminuria is an inherited autosomic recessive disease due to mutations in the human FMO3 gene. High levels of free TMA in urine and other body fluids confer an unpleasant body odor resembling that of fish. Here we report a case of primary trimethylaminuria in a 4-year-old girl.

PATIENT AND METHOD

A 4-year-old girl who presented with a strong corporal scent resembling that of fish from the age of 9 months agreeing with the introduction of fish in the diet. The patient did not have other relevant personal history and had a correct psychomotor and growing development. Liver function, urea and creatinine levels were normal. The biochemical diagnosis was done by spectrometry, measuring the amount of TMA and TMA-O prior to and after fish intake.

RESULTS

Genetic analysis evinced that the patient was homozygous for a novel mutation in exon 3, R51G (c. 151A > G). Both parents were heterozygous.

CONCLUSIONS

R51G (c. 151 A > G) mutation had not been found in other patients with trimethylaminuria.

Amish lethal microcephaly: a new metabolic disorder with severe congenital microcephaly and 2-ketoglutaric aciduria

A new metabolic disorder characterized by severe congenital microcephaly, death within the first year, and severe 2-ketoglutaric aciduria has been found among the Old-Order Amish of Lancaster County, Pennsylvania. Amish lethal microcephaly segregates as an autosomal recessive disorder and has an unusually high incidence of at least 1 in 500 births. When the infants are well, the urine organic acid profiles show isolated, extreme elevations of 2-ketoglutaric acid. However, during otherwise simple viral illnesses, the infants often develop a metabolic acidosis, which may follow a lethal course. Cranial magnetic resonance imaging of a single patient showed a smooth, immature brain similar to that of a 20-week fetus except for a moderate degree of cerebellar vermal hypoplasia. Assay of 2-ketoglutarate dehydrogenase in cultured lymphoblasts of one patient showed normal activity. Amish lethal microcephaly maps to 17q25 and may be caused by a defect in a mitochondrial inner membrane protein functioning as a 2-ketoglutarate transporter.

Measurement of corticoids in the patients with clinical features indicative of mineralocorticoid excess

BACKGROUND

A method for the measurement of five important serum and urinary corticoids on the syndrome of mineralcorticoid excess is reported. The methodology was combined gas chromatography-mass spectrometry (GC-MS) with selected ion-monitoring mode.

METHODS

After extraction with a solid-phase cartridge using an Oasis HLB copolymer, the residues were derivatized with a mixture of N-methyl-N-trimethylsilyltrifluoroacetamide/ammonium iodide/dithioerythritol (1000:4:5, v/w/w), and analyzed.

RESULTS

The linearity as the regression coefficients were >0.979 over a range of 1-500 ng/ml, and limit of detection ranged from 1 to 3 ng/ml while their analytical recoveries varied in the range of 75.7-94.9%. The overall precision (% CV) of the method were 3.2-7.2% and 3.6-6.3% for serum and urine, respectively. The accuracy expresses as % bias ranged from -4.1 to 6.4%. This assay was used on two patients with hypokalemic hypertension, and may be useful in ruling out mineralcorticoid excess (AME) type 1 or 2.

CONCLUSIONS

The present GC-MS technique may be useful to differentiate between the syndrome of AME and other hypertensive diseases with clinical features suggestive of mineralcorticoid excess because of the assay's reliablity and precision.

Glutaryl-CoA dehydrogenase deficiency in Spain: evidence of two groups of patients, genetically, and biochemically distinct

Glutaryl-CoA dehydrogenase (GCDH) deficiency causes glutaric aciduria type I (GA I), an inborn error of metabolism that is characterized clinically by dystonia and dyskinesia and pathologically by neural degeneration of the caudate and putamen. Studies of metabolite excretion allowed us to categorize 43 GA I Spanish patients into two groups: group 1 (26 patients), those presenting with high excretion of both glutarate and 3-hydroxyglutarate, and group 2 (17 patients), those who might not be detected by routine urine organic acid analysis because glutarate might be normal and 3-hydroxyglutarate only slightly higher than controls. Single-strand conformation polymorphism (SSCP) screening and sequence analysis of the 11 exons and the corresponding intron boundaries of the GCDH gene allowed us to identify 13 novel and 10 previously described mutations. The most frequent mutations in group 1 were A293T and R402W with an allele frequency of 30% and 28%, respectively. These two mutations were also found in group 2, but always in heterozygosity, in particular in combination with mutations V400M or R227P. Interestingly, mutations V400M and R227P were only found in group 2, and at least one of these mutations was found in 11 of 15 unrelated alleles, accounting together for 53% of the mutant alleles in group 2. Therefore, it seems clear that two genetically and biochemically distinct groups of patients exist. The severity of the clinical phenotype seems to be closely linked to the development of encephalopathic crises rather than to residual enzyme activity or genotype. Comparison of GCDH protein with other acyl-CoA dehydrogenases (whose x-ray crystal structure has been determined) reveals that most of the mutations identified in GCDH protein seem to affect folding and tetramerization, as has been described for a number of mutations affecting mitochondrial beta-oxidation acyl-CoA dehydrogenases.

Screening for pyrimidine metabolism disorders using dried filter-paper urine samples: method development and a pilot study in Nagoya City, Japan

A screening system for pyrimidine metabolism disorders by measurement with high-performance liquid chromatography using dried filter-paper urine samples is presented. This system permits the simultaneous determination of dihydrouracil, uracil, orotic acid and pseudouridine. The coefficient of variations for the four compounds on the filter-paper urine samples were 0.010 approximately 0.069 and the recoveries were 98.5 approximately 107.1%. The detection limits of the four compounds were 2 approximately 20 micromol/liter. The correlation between the filter-paper urine samples and liquid urine samples was excellent (0.938-0.988). We supeculated that this method could be used to detect pyrimidine metabolism disorders, such as dihydropyrimidinuria, dihydropyrimidine dehydrogenase deficiency and hereditary orotic aciduria. As a pilot study, we have analyzed dried filter-paper urine samples from 34, 200 healthy Japanese, and found three cases of dihydropyrimidinuria without clinical symptoms.

Prevention of cerebral palsy in glutaric aciduria type 1 by dietary management

AIMS

To study retrospectively the effects of treatment and the clinical outcome in 12 patients with glutaric aciduria type 1; and to compare the outcome in 6 patients diagnosed as a result of family screening with 6 patients who were diagnosed late after symptomatic presentation.

SETTING

The National Centre for Inherited Metabolic Disorders, The Children's Hospital, Dublin, Ireland.

RESULT

Four of the 6 children detected on screening are developmentally normal, 1 died, and the remaining 1 has mild mental handicap. All 6 of the late diagnosed symptomatic group suffered dyskinetic cerebral palsy and 5 have died.

CONCLUSION

Experience of 50 patient treatment years has shown that early intensive management can alter the natural history of this rare disorder.

Fish odor syndrome

Fish odour syndrome (trimethylaminuria) is a metabolic syndrome caused by abnormal excretion of trimethylamine in the breath, urine, sweat, saliva and vaginal secretions. Trimethylamine is derived from the intestinal bacterial degradation of foods rich in choline and carnitine and is normally oxidised by the liver to odorless trimethylamine N-oxide which is then excreted in the urine. Impaired oxidation of trimethylamine is thought to be the cause of the fish odour syndrome and is responsible for the smell of rotting fish. Certain foods rich in choline exacerbate the condition and the patients have a variety of psychological problems. Recognition of the condition is important as dietary adjustments reduce the excretion of trimethylamine and may reduce the odour. Occasionally, a short course of metronidazole, neomycin and lactulose may suppress production of trimethylamine by reducing the activity of gut microflora.

Analysis of diagnostic metabolites by capillary electrophoresis-mass spectrometry

We describe here a procedure by capillary electrophoresis-mass spectrometry (CE-MS) for the direct analysis of urine samples on diagnostic metabolites, which are present in patient urine with metabolic disorders. The method was demonstrated using urine samples spiked with diagnostic metabolites, including glutathione for gamma-glutamyl transpeptidase deficiency, pyroglutamate for generalized glutathione deficiency, adenylosuccinate for adenylosuccinase deficiency, omithine for gyrate atrophy, histidine for histidinemia, and homogentisic acid for alcaptonuria, at concentrations similar to those found in patients' urine. A coaxial sheath liquid flow was used for coupling CE and MS in electrospray ionization mode. Identification of the metabolites is based on their molecular weights and fragmentation patterns. The CE-MS method is highly specific and sensitive comparing to the previously reported method using migration time and UV absorption for identification. It should find broad application in clinical and pharmaceutical research and development.

The occurrence of post-gamma protein in urine: a new protein abnormality

As a result of studying the urine proteins of 223 individuals by starch gel electrophoresis, a new urine protein fraction has been recognized. On starch gel electrophoresis at alkaline pH the new fraction moves to a position appreciably nearer the cathode than the slowest-moving gamma-globulin in normal serum. A small amount of this post-gamma protein was found in the urine of 46 patients with clinical proteinuria, including 19 with the Fanconi syndrome and nine with multiple myeloma. The nature, origin, and clinical significance of post-gamma protein is discussed.